A fuel cell is a kind of generator that electrochemically reacts chemical energy of fuel in a stack to convert the chemical energy into electric energy. The fuel cell may be used to supply not only driving power for industry, home and vehicles but also power for handheld electronic devices, such as portable devices. Recently, the use field of the fuel cell is being gradually expanded as a clean energy source with high efficiency.
FIG. 1 is an exploded perspective view illustrating a conventional fuel cell stack.
As illustrated in FIG. 1, the conventional fuel cell stack includes a membrane electrode assembly (MEA) 4 that has an electrolyte membrane and electrodes disposed on both surfaces thereof, a pair of gas diffusion layers (GDL) 6 that are attached to the electrodes of the membrane electrode assembly and aid in diffusing reactive gases, a separator 8 that is in close contact with each gas diffusion layer to supply the reactive gases, and a gasket 8a that prevents the leakage of the reactive gases.
The separator 8 prevents hydrogen and oxygen, which are reactive gases, from being mixed with each other, and is electrically connected to the membrane electrode assembly 4 to support it, thus serving to maintain the shape of the fuel cell stack.
Thus, the separator 8 should be delicate in structure to prevent reactive gases from being mixed with each other, and should have high strength as well as high conductivity to serve as a conductor and a support. Thereby, the separator 8 made of metal material is mainly used.
Since voltage generated from one unit cell 2 having the membrane electrode assembly 4, the gas diffusion layer 6, the gasket 8a, and the separator 8 is low, a plurality of unit cells is stacked and used depending on required voltage.
However, in the case of stacking many unit cells 2 as such, the separator 8 does not maintain a uniform surface pressure, thus causing local deformation, or does not maintain sealing.
Further, in order to fix the plurality of stacked separators 8, spot welding or laser welding is used. However, the corrosion resistance of a welded part is low, so that the welded part may be possibly corroded, and the welded part is lower in strength than a peripheral part, so that cracks or the like may be generated.
Particularly, when the thickness of the separator 8 is 0.1 mm or less, deformation may be caused by pressure during welding, and stackability is deteriorated.
In order to improve the stackability of the conventional separator 8, technology has been developed, in which uneven parts for fitting are formed on both sides of the separator 8 to improve the stackability. However, the above-mentioned method is problematic in that it is necessary to secure height that is sufficient for the uneven part to form a shape for fitting, and the separator 8 of 0.1 mm or less may be deformed or cracked in a pressing operation for fitting the uneven part.
The foregoing is intended merely to aid in the understanding of the background of the present invention, and is not intended to mean that the present invention falls within the purview of the related art that is already known to those skilled in the art.